Various kinds of the powders of metals, metal oxides, metal nitrides, metal silicides, and their mixed compounds have been used as the crude starting materials to produce such materials as magnets, catalysts, electrodes, batteries, heat insulators, refractory substances, and sintered metals. Such powders commonly suffer from poor uniformity of composition, shape, granularity and for spherical powders, poor sphericity (degree of roundness). A mechanical pulverization apparatus is capable of producing particles that have fine structure and are composed of more than two types of components. While of possibly uniform composition, such particles are of poor uniformity in size and shape, and of course are not of spherical shape. Moreover, it is difficult to obtain a nanocomposite structure using mechanical pulverization for the production of fine powders.
The apparatuses, systems and self assembling processes of the present invention provides for the production of very small, spherical particles having a nano-composite structure which is a particularly important embodiment of the present invention having high utility as strong permanent magnetic powders. Conventional apparatuses and methods can not result in a nanocomposite magnetic material at all, and certainly not result in the present tiny spherical powders by a self-assembly technique.
For example, materials for permanent magnet are disclosed for example in Japanese patent publication Hei 7-78269 (Japanese patent application Sho 58-94876, the patent families include U.S. Pat. Nos. 4,770,723; 4,792,368; 4,840,684; 5,096,512; 5,183,516; 5,194,098; 5,466,308; 5,645,651), which discloses (a) RFeB compounds containing R (at least one kind of rare earth element including Y), Fe and B as essential elements and having a tetragonal crystal structure with lattice constants of ao about 9 Å and co about 12 Å, and each compound is isolated by non-magnetic phase, and (b) RFeBA compounds containing R, Fe, B and A (A=Ti, Ni, Bi, V, Nb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge, Sn, Zr, Hf, Cu, S, C, Ca, Mg, Si, O, or P) as essential elements and having a tetragonal crystal structure with lattice constants of ao, about 9 Å and co about 12 Å, and each compound is isolated by non-magnetic phase. Though this magnet shows excellent magnetic properties, the latent ability of the RFeB or RFeBA tetragonal compounds have not been exhibited fully.
U.S. Pat. No. 5,942,053 provides a composition for permanent magnet that employs a RFeB system tetragonal tetragonal compounds. This magnet is a complex of (1) a crystalline RFeB or RFeCoB compounds having a tetragonal crystal structure with lattice constants of ao about 8.8 Å and co about 12 Å, in which R is at least one of rare earth elements, and (2) a crystalline neodymium oxide having a cubic crystal structure, wherein both crystal grains of (1) and (2) are epitaxially connected and the RFeB or RFeCoB crystal grains are oriented to the co direction. While the resulting magnet has very good magnetic properties, no effort was made to control the nanostructure of the composition and thus the U.S. Pat. No. '053 magnet does not employ the nano-sized and non-magnetic material, neodymium oxide that is incorporated at the inside of the NdFeB ferromagnetic grains and/or at their grain boundaries as in the present invention. The U.S. Pat. No. '053 magnet does not employ the nanostructure consisting of micro-sized ferromagnetic phase and nano-sized nonmagnetic phase resulting in the nanocomposite structure of the present invention.
Conventional apparatuses for producing metal spheres include means for melting the metal and pouring the metal upon a rotating base that flings the molten metal to form spheroid particles. See JP 51-64456, JP 07-179912, JP 63-33508 and JP 07-173510. Such typical atomization apparatuses produce spherical powders having poor sphericity, limited microdimensions and poor uniformity of composition and shape. The methods and apparatuses of the present invention provide for producing particles of extremely small, highly uniform spherical shape, further providing for particles having nanocomposite structures by self-assembly of such structure.